1. Field of the Invention
The present invention relates to a multi-direction-operative key switch used as a scroll key and a navigation button in electronic appliances such as portable telephones, and to a new structure of a multi-direction-operative key that is a push button mechanism of the multi-direction-operative key switch.
2. Descriptions of the Related Art
xe2x80x9cA multi-direction-operative key switchxe2x80x9d is a composite switch which is capable of inverting on/off a switch element by tilting a key forward and backward or to the left and right as well as by pushing the key vertically, and which operates a plurality of switch elements separately by a single key. If specified functions are respectively allocated to the respective switch elements, a manipulation for selecting and determining one or more functions among the plural functions can be speedily performed with one fingertip.
xe2x80x9cA multi-direction-operative keyxe2x80x9d is a push button mechanism for manipulating the multi-direction-operative key switch. The multi-direction-operative key is a part of a component called xe2x80x9ca key sheetxe2x80x9d that is an aggregate composed of many keys. The multi-direction-operative key is combined with a printed-circuit board and the like, on the surface of which many switch elements are arranged, whereby xe2x80x9ca multi-direction-operative key switchxe2x80x9d is formed on the portion of the key sheet and the printed-circuit board.
The multi-direction-operative key is composed of xe2x80x9ca key topxe2x80x9d that is a portion manipulated directly by a finger, and a flexible xe2x80x9ckey basexe2x80x9d that transmits a motion of the key top to the switch elements while keeping the key top at a predetermined position. On a lower plane of the key base, a switching pressurizing projection so called a thruster is respectively formed by one at a position just below the center of the key top and at a position slanted from the key.
The printed-circuit board and the like, which are combined with this multi-direction-operative key, are provided so as to contact with the lower plane of the key base, and the switch elements are arranged at the respective positions facing the tips of the switching pressuring projections. Note that these switch elements should transmit its slight vibrations called a click feeling to the key top so that the finger can feel the operation.
On the other hand, there has been a multi-direction-operative key based on an operation principle different from that of the foregoing one, which is called, for example, an analog input type. For example, the one which detects the key""s motion as a change of electrostatic capacitance. This kind of multi-direction-operative key detects the motion of the key as continuous variables not as binaries of on and off. Moreover, this multi-direction-operative key can detects not only the motion in the forward and backward directions and in left and right directions but also the slant motion in any direction. Focusing attention on such characteristics, the multi-direction-operative key is used for joysticks for game machines. However, in terms of its structure, it is impossible to make the operator feel the click feeling by adding elements such as metal domes, and it cannot be estimated that this multi-direction-operative key is suitable for portable telephones and the like. Note that, in contrast with this analog input type key, the one using the switch elements is sometimes called xe2x80x9ca contact-having multi-direction-operative key (switch)xe2x80x9d.
Since the conventional contact-having multi-direction-operative key switch has only one switch element in each direction in which the key inclines, only binary signals having [0,1] as a variable range in that direction can be input. Moreover, different result cannot be obtained even if the key is inclined either rapidly or slowly, and a speed at which the key is inclined cannot be used as a signal. On the other hand, though there is no such a limitation in the analog input type key, the analog input type key is not suitable for the portable telephone and the like as described above.
An end of the present invention is to provide an improved contact-having multi-direction-operative key switch which is capable of inputting multi-valued signals thereto by slanting operation of a key. Another object of the present invention is to propose a structure of a multi-direction-operative key suitable for this end.
The end of the present invention is achieved by a multi-direction-operative key which comprises a key top made of hard resin; a key base made of rubber-like elastic body loading the key top on its surface; and a plurality of switch pressuring projections, each of which is made of the same material as that of the key base and extends vertically from a rear surface of the key base opposite to the surface loading the key top, wherein the switch pressuring projections are respectively provided at the position just below the center of the key top and at intersection points of a plurality of concentric circles surrounding the center of the key top and radii of the key top in its inclination directions, and lengths of the switch thrusting projections in the inclination directions are made to be different for the concentric circles.
Structural features of the multi-stage multi-direction-operative key according to the present invention are that the plurality of switch pressuring projections (that is, the multi-stage switch pressuring projections) are provided in one inclination direction of the key top, and the lengths of the projections are different from each other. In addition, each projection is formed of flexible rubber-like elastic body identical to that of the key base. Note that switch elements combined with this multi-stage multi-direction-operative key shall be arranged on a printed circuit board placed below the key base parallelly.
In the multi-stage multi-direction operative key constructed as above, when the key is inclined, the switch pressuring projection having the largest length in a certain inclination direction of the key top first pushes the corresponding switch element. However, since other switch thrusting projections are short, their tips do not touch the corresponding switch elements. If the key top is further inclined, the switch pressuring projection which touched the switch element earlier is crushed due to its elastic deformation, and the projection having the secondly largest length comes to push the corresponding switch element. Accordingly, the number of the switch elements turned on differs depending on the magnitude of force applied to the key top to incline it. Since the number of the switch elements is a multi-value variable having [0, 1, . . . n] as a variable range, the multi-valued signal will be input. Herein, numeral n is the number of the switch thrusting projections (switch elements) in a certain inclination direction of the key top.